Insofar as is known, very little development work has been done in the field of collapsible reels.
U.S. Pat. No. 1,832,590 issued Nov. 17, 1931 in the name of Earl I. Sponable et al. discloses a collapsible reel for movie film in which the reel is divided into two rigid semicircular segments pivotably connected at their bottoms and coupled together at their tops by mechanism comprising a pair of toggle members, each having one end thereof pivotably coupled to a respective one of said segments, the other end of each such member being pivotably coupled by a pin to the other toggle member. Radially outward movement of the pin acts through the toggle members to spread apart the tops of the reel segments, while radially inward pin movement draws those tops together. A spring is used to bias the pin to its radially outward position.
U.S. Pat. No. 2,074,217 issued Mar. 16, 1937 to T. Grover discloses a carrier for freshly spun threads of artificial silk in which the thread is wound on a plurality of parallel rods spaced around the insides of two spaced coaxial discs to form a circular array of such rods, the rods being slidably mounted at their ends by such discs to be radially movable in an out. The rods are biased radially outward from their inner side by a resilient spring curved into annular shape such that the two ends of the spring are adjacent. Those two ends are coupled together by mechanism comprising a toggle joint of a link and a central arm pivotally connected together, and each coupled through another pivotal connection at an end thereof to a respective one of those spring ends. The central arm is extended beyond its pivotal connection with the link to provide a handle which can be moved inward from a normal to an actuated position. When the handle is in normal position, the ends of the spring are fully spread apart to drive the mentioned rods radially outwards to the fullest. Radial inward movement of the handle to actuated position causes the ends of the spring to be drawn together to thereby permit the rods to move radially inward.